Marek's disease virus (MDV) is a herpesvirus, which causes lymphoproliferative disease in chickens. Even after the introduction of vaccines against MDV, the infection still causes considerable losses in the poultry industry. MDV is divided into three serotypes, all of which establish latent infections. Serotype 1 includes oncogenic viruses, serotype 2 non-oncogenic viruses and serotype 3 includes the turkey herpesviruses (HVT) (Bülow et al (1976) Zentralblatt für Veterinarmedizin, 23B, 391-402).
The traditional diagnosis of Marek's disease is based on the clinical signs and pathological alterations. However, more specific methods for surveillance of the prevalence of MDV would be desirable. The detection of viral antigen in the feather follicle epithelium by the agar gel precipitation test has been described by Haider et al (1970) Poultry Science, 49, 1654-1657. The different serotypes can be differentiated by the agar gel precipitation test (Lee et al (1983) Journal of Immunology, 130, 1003-1006), but the sensitivity of that test is inferior to that of enzyme-linked immunosorbent assay (ELISA) and DNA hybridization (Davidson et al (1986) In: Current research on Marek's disease. Proceedings of the 5th International Symposium on Marek's Disease (pp. 311-316). Tallahassee: Rose Printing Company, Inc.).
The preferred samples for virus isolation are buffy-coat cells, which can be co-cultivated with susceptible primary cell cultures. Immunofluorescent assay (Kitamoto et al (1979). Biken Journal, 4, 137-142) or ELISA (Cheng et al (1984) Avian Diseases, 4, 900-911), can be used for subsequent identification of the MDV serotype. Alternatively, the serotype can be identified by restriction endonuclease analysis (Ross et al (1983). Journal of General Virology, 64, 2785-2790) or polymerase chain reaction (PCR) (Wang et al (1993) Molecular and Cellular Probes, 7, 127-131. In situ hybridization has been used for detection of MDV genome in infected tissue (Endoh et al (1996) Journal of Veterinary Medical Science, 58, 969-976; Ross et al (1997) Journal of General Virology, 78, 2191-2198), but this technique is probably too laborious for routine diagnoses. (Davidson et al (1995) Avian Pathology, 24, 69-94; and Davidson et al (1996) In: Current research on Marek's disease. Proceedings of the 5th International Symposium on Marek's Disease (pp. 311-316). Tallahassee: Rose Printing Company, Inc.), applied MDV serotype 1-specific PCR techniques to full blood and tumour tissue samples from commercial chicken and turkey flocks, the majority of which had neoplastic disease. Wang et al (1993) Molecular and Cellular Probes, 7, 127-131; Young, P. & Gravel, J. (1996) In Current research on Marek's disease. Proceedings of the 5th International Symposium on Marek's Disease (pp. 308-310). Tallahassee: Rose Printing Company, Inc.; and Silva, R. F. & Witter R. L. (1996) In Current research on Marek's disease. Proceedings of the 5th International Symposium on Marek's Disease (pp. 302-307). Tallahassee: Rose Printing Company, Inc., applied a MDV serotype 1-specific PCR protocol to various tissues of chickens experimentally inoculated with the JM/102 strain.
Handberg et al (2001) Avian Pathology 30: 243-249 describe the use of serotype 1- and serotype 3-specific PCR for the detection of MDV in chickens. Tissue samples were taken from blood (buffy-coat cells), spleen, liver, skin, feather tips and ovaries.